Displacement pump



DEC. 4, 1934. V H H|L ER ET AL 1,983,229

DI SPLACEMENT PUMP Filed Oct. 21, 1953 4 sheet t 1 Fml.

Dec. 4, 1934. H H L E 5 A 1,983,229

DISPLACEMENT PUMP Filed Oct. 21, 1933 4 Sheets-Sheet 2 Dec. 4, 1934. H HILUER H M 1,983,229

DI SPLACEMENT PUMP Filed Oct. 21, 1933 4 Sheets-Sheet 3 Dec. 4, 1934. i H, H|LL|ER r AL 1,983,229

DI S PLAC EMENT PUMP Filed Oct. 21, 1935 4 s t -s t 4 @stented; Dec. 4, 1934 UNETED s 'rss PATENT V FECE' msrmommm' Pom Allan ted, Glasgow, Great Britain Application October 21, 1933, Serial N James Colquhoun Masha-lane,

Macfarlane, Cathcart,

Scotland, assignors to G. & .l'. Weir, Scotland, a corporation of In Great Britain November: d, 1932 intention relates to displacement pumps the comprising a pair of cc-acting disvilcceis, such as plungers, actuated by separate crank-shafts, and working in 5. common chamber, or .urality of ioairs of co-acting displacers, cool: air working in a common chamber the volumetiic discharge from which chamber or circle oi chambers is varied by varying the phase relation of the crankshaz' when the crankshafts are chase, the v umetric displacement is the maximum; when e crankshafts are in opposite phase relation,

known to drive the two crankshaft-s by .eans of two synchronous motor and to vary the l ive timing of the two crankshafts by partially rotating the stator of one motor so as to alter the position of the poles of said stator relatively to thenoles of the stator of the other motor, and thereby to alter the relative timing of the two nlrshaits.

In the p 2 according to the present invention he csanlzshafts are normally driven at equal speeds icy motors having fixed stators, associated with means controlled by the delivery pressure of the and adapted momentarily to bring variable .elivery displacement pump driven by two induction motors coupled to D. C. machines,

. the changers being shown in phase corresponding I motor to mecziimmi delivery. Fig. 2 shows diagramstatically the same pump as in Fig. l but with the nt gers in opposite phase corresponding to um delivery. Fig. 3 shows a modified can merit of the hunting controller. Fig. 4 shows a further modified arrangement of the hou ing'contrcller. Fig. 5 shows diagrammatian arrangement incorporating a slip-ring lg a variable rotor resistance, the plungci's be cg shown in phase. Fig. 6 is a. view similar to Fig. 5 but with the plungers shown out of phase. Fig. '7 is a fragmentary view showing a further modification incorporating two slipring induction motors with variable rotor resistances.

Referring to Figs. 1 and 2 of the drawings, 1 and 1a denote two co-acting plungers driven by separate crank shafts 5 and 5a, respectively, and adapted to operate in a common chamber 2 provided with a suction valve 3 and with a discharge valve 4. As shown in Fig. 1, the crankshatts 5 and 5a are in phase'so that the volumetric displacement of the plungers l and lais the maxi The crankshafts 5 and 5a are driven normally at equal speeds through gearing 7 and m by induction sectors 6 and 6a which are preferably of the squirrel-cage type. iliircctly coupled to the motors 6 and 6a are two D. C. machines 3 and 5a the armatme circuits of which are coupled in opposition, so that with equal fields the some voltage is generated in each and no current flows. The delivery pressure in the pump discharge pipe 9 acts on one end of a piston lo opposition to a spring 11 acting on the other end of said piston 16. A spindle 12 attached to the piston to is oneratively connected to the sliding contact of a potentiometer is.

The craukshafts 5 and 5a drive bevel wheels 1 and 15a, shafting, and bevel wheels 16 and 16a of a clifi'erential gear. Meshing with the bevel wheels and 16a are two intermediate bevel wheels 1'? and i8 jomnalled in a casing 19 rotatable about th common axis of the bevel Wheels 16 and 16s and presenting a cam 20 cooperating with a follower on aspindle 21 connected to the potentiometer is. The potentiometer resistor is coupled in series with the fields 22 22a of the D. 0. machines 8 8a, the brushes of which machines are coupled to form 9. circuit 23 electrically connected to the contact 13 of the potentiometer 14.

With the contact 13 in mid position with respect to the resistor the voltage generated by the machine 8 is equal to the voltage generated by the machine 8a and no current flows in the circuit 23. If, however, the contact '13 is moved to unbalance the resistance, for example to insert additional resistance in the field 22, and to cut out resistance from the field 22a, the D. C. machine So becomes a generator while the D. C. machine 8 becomes a motor, thus transferring power from the shaft of the induction motor 611 to the shaft of the induction motor 6. The efiect is to increase the speed of the armature of the induction motor 6 and to reduce the speed of the armature of the induction motor So, so that the crankshafts 5 and 5a are diflerentially speeded to bring about variation in the relative timing of said crankshafts and so vary the volumetric displacement of the plungers l and la.

When the crankshafts 5 and 5a are differentially speeded, the bevel wheel drive 15 and 15a causes the casing 19 partially to rotate the cam 20 and thereby displace the potentiometer 14 until the contact 13 is again at the mid-point of the resistor, when the resistances in the fields 22 and 22a will again be equal. No current will then flow in the circuit 23, the D. C. machines 8 and 8a will generate equal voltages, and the armatures of the motors 6 and 6a will again rotate at equal speeds, the crankshaits 5 and So being now out of phase.

Fig. 2 shows the plungers in the opposite phase position corresponding to minimum pump delivery. It will be understood that, by varying the phase relation of the two crankshafts .5 and 5a between the position shown in Fig. 1 and the position shown in Fig. 2, any pump delivery between maximum capacity and minimum capacity can'be obtained. The pressure in the pump delivery pipe 9 controls the position of the piston 10 which is the first part of the hunting controller, movement of the piston 10 being communicated to the potentiometer contact 13 which causes the requisite differential speeding of the armatures of the motors 6 and 6a to produce the'required change shown in Fig. 1, when the crankshafts 5 and 5a' are in phase, the cam 20 is in its maximum throw position and the piston 10 is in its uppermost or minimum delivery pressure position. Conversely, and as shown in Fig. 2, when the crankshafts 5 and 5a are in opposite phase, the cam 20 is in its minimum throw position and the piston 10 is in lowermost or maximum delivery pressure position.-

Thus, in the construction according to Figs. 1 and 2, the delivery pressure will fall continuously from minimum pump output corresponding to the opposite phase position shown in Fig. 2 to maximum pump output corresponding to the in-phase position shown in Fig. 1, so that the pressure capacity characterismc of ,the'pump will fall continuously from no load to full load.

In the modification shown Fig. 3 the cam 20 of the hunting controller is so arranged that the delivery pressure of the pump will rise continuously from no load to full load and the pressure capacity characteristicof the pump will closely approximate to the resistance capacity characteristic of the delivery system, the power required to drive the pump being thereby reduced to the minimum for all capacities.

In this arrangement the spindle 21 acts on one.

end of a floating lever 13 carrying the contact 13, the other end of said lever being operated by the piston 10 through the spindle 12. The lever 13 holds the contact 13 atmid position of the potentiometer when a given pump output corresponds to the predetermined delivery pressure for that output.

With a, fall in pressure the piston 10 and spindle 12 rise, and raise the. contact 13 relatively to the resistance 14. In consequence, the output of the pump will be increased until the spindle 21 is lowered and lowers the contact 13 to mid position. Conversely, with rise in pressure the piston 10 and spindle 12 will be lowered, the contact 13 will be lowered relatively to the resistance 14, and the output of the pump decreased.

Fig. 4 shows an alternative arrangement of the hunting controller to obtain a rising pressure capacity characteristic. The position of the spindle zl actuated by them 20 determines the position ofthe spring base 21a in accordance with the relative timing of the crankshafts. For any given "pump output is increased due to the rise of the contact 13, the base 21a is displaced in the direction to restore the contact 13 to mid position whereupon the pump continues to run at increased output. 'Oppositely directed movements of the contact 13 and base 21a are brought about by an increase in delivery pressure due to the output being greater than the demand.

In the construction according to Fig. 3 or Fig. 4 the cam 20 is in its maximum throw position as shown when the crankshafts are in phase giving maximum output, when the piston 10 is fully depressed under maximum delivery pressure, and when the contact 13 is positioned at the mid point of the potentiometer 14. Conversely, when the cam 20 is in minimum throw position correspond-- ing to minimum output, with the contact 13 at mid position, the piston 10 will be located in fully raised position corresponding to minimum delivery pressure. Manifestly, either arrangement is such as to produce a rising pressure capacity characteristic incontradistinctiun to the arrangement according to Figs. 1 and 2 as evidenced by the relative positions-of the cam 20, contact 13 and piston 10 as shownin these figures.

While there hasbeen described a differential gear driven by the crankshafts as constituting the operating mechanism of the second part of thehunting controller, it will be understood that the second part of the hunting controller may be actuated by any portion of: the electrical or driving mechanism having a definite position for any given relative timing of the crankshafts, i. e., operating in synchronism with the :change of relative timing of the crankshaits.

The second part of the hunting, controller may comprise electrical devices. For example, the armature speeds of the driving motors are equal when there is no flow of ru rrer'it through the circuit 23, whereas, when the, armatures are differentially speeded, there is a flow of current through the circuit 23 and thisffiow may be utilized to operate a'motor, solenoid, or other device for the purpose of restoring the potentiometer to equilibrium position aftera movement of the potentiometer effected by the first part of the hunting controller. 4

Referring to Figs. 5 and driven by a squirrel-cage motor 26 having a relatively high resistance rotor running at a sub; stantially constant speed. The crankshaft 5 is driven by a slip-ring induction motor 25 the rotor circuit of which is provided withavariable resistor 27, so that by variation of the resistance in the rotor circuit, due to movement of the contacts 28, caused by a change in delivery pressure in the pipe 9 acting on the piston 10, the speed of the rotor of the motor 25 is increased or reduced relatively to the speed of the rotor of the motor 26 for the period of time necessary to change the relative timing of the crankshafts 5 and 5a to bring about the requisite change in pump output. Any movement of the piston 10, which is the first part of the hunting controller, varies 6, th'e crankshaft 5a is theresistanceandcauses avariationintherelative timing of the two crankshafts by diiferentially speeding the rotors of the two motors 25 and 26, while the changing of the relative timing of the two crankshafts causes the second part of' the hunting controller, comprising the parts 15 to 21, to restore the resistor to the podtion at which the speed of the armature of the slip-ring motor 25 is equal to the speed of the rotor of the squirrel-cage motor 26 with the pump output modified as required by the delivery pressure.

As shown in Fig. 7 both motors 25 and 26a are of the slip-ring induction type with variable rotor resistances 27, 27a arranged to increase the speed of the rotor of the motor 260 when the speed of the rotor of the motor 25 is being reduced and to decrease the speed of the rotor of the motor 26a when the speed of the rotor of the motor 25 is being increased.

It should be understood that the structure shown in Fig. 7 will be equipped with a differential follow-up mechanism such as is shown in the other figures of the drawings.

What we claim is:

1. In a displacement pump, in combination, a displacement chamber, at least one pair of displacers working in said chamber, separate shafts for driving said displacers, motors having fixed stators and rotors normally rotating at equal speeds for driving said shafts, and means controlled by the pressure of the discharged fluid and adapted momentarily to cause differential speeding of said rotors to vary the relative timing of said shafts.

2. In a displacement pump, in combination, a displacement chamber, at least one pair of displacers working in said chamber, separate shafts for driving said displacers, a substantially constant speed motor driving one of said shafts, a motor having a fixed stator and a variable speed rotor adapted normally to drive the other of said shafts at the same speed as the first mentioned shaft, and means controlled by the pressure of the discharged fluid for momentarily varying the speed of said rotor to change the relative timing of said shafts. I

3. In a displacement pump, in combination, a displacement chamber, at least one pair of displacers' working in said chamber, separate shafts for driving said displacers, motors having rotors normally rotating at equal speeds for driving said shafts, and means for momentarily causing differential speeding of said rotors to vary the rel ative timing of said shafts, said means comprising a part controlled by the pressure of the discharged fluid, and a part controlled in synchronism with the variation of the relative timing of said shafts.

4. In a displacement pump, in combination, a displacement chamber, at least one pair of displacers working in said chamber, separate shafts driving said displacers, motors having armatures rotating normally at equal speeds for driving said shafts, and means for initiating and then discontinuing differential speeding of said armatures to vary the relative timing of said shafts, said means giving a delivery pressure falling from a maximum at zero discharge to a minimum at maximum discharge, and comprising a part controlled by the pressure of the discharged fluid and a part controlled in synchronism with the variation of the relative timing of said shafts.

5. In a displacement pump, in combination, a displacement chamber at least one pair of displacer-s working in said chamber, separate shafts driving said displacers, motors having armatures normally rotating at equal speeds for driving said shafts, and means for initiating and :then discontinuing diiferential speeding of said armatures to vary the relativetiming of said shafts, said means giving a delivery pressure rising from a minimum at zero discharge to a maximum at maximum discharge, and comprising a part controlled by the pressure of the discharged fluid and a part controlled in synchronism with the variation of the relative timing of said shafts.

6. In a displacement pump, in combination, a displacement chamber, at least one pair of displacers working in said chamber, separate shafts driven by said displacers, motors for rotating said shafts normally at equal speeds, means controlled by the pressure of the discharged fluid for initiating differential speeding of said motors to vary the'relative timing of said shafts, a differential gear including a member responsive to variation in the relative timing of said shafts, and means cooperative with said member for restoring the relative speeds of said motors.

7. In a displacement pump, in combination, a

placement chamber, at least one pair of displacers working in saidchamber, separate shafts driving said displacers, motors for rotating said shafts normally-at equal speeds, D. C. machines coupled to said motors and having armature oircults connected in opposition, a potentiometer controlling the field circuits of said machines, and means comprising a device responsive to the pressure of the discharged fluid and acting on said potentiometer to initiate diflerential speed- 11; ing of said motors to vary the relative timing of said shafts, and mechanism responsive to variation of the relative timing of said shafts and acting on said potentiometer in opposition to said device to restore equality of speeds of said motors.

8. In a displacement pump, in combination, a displacement chamber, at least one pair of displacers working in said chamber, separate shafts driving said displacers, a substantially constant speed motor driving one of said shafts, a slip- :20 ring induction motor with variable rotor resistance driving the other of said shafts normally, at the same speed as the first shaft, means comprising a device responsive to the pressure of the discharged fluid for varying the speed of said induction motor to vary the relative timing of said shafts, and mechanism responsive to variation of the relative timing of said shafts and operating in opposition to said device to vary said rotor resistance to discontinue the difierential speed- 9 ing of said motors.

9. In a displacement pump, in combination, a displacement chamber, at least one pair of displacers working in said chamber, separate shafts driving said dlsplacers, slip-ring induction motors with variable rotor resistances driving said shafts normally at equal speeds, and means comprising a device responsive to the pressure of the discharged fluid for varying said rotor resistances whereby to initiate differential speeding of said motors to vary the relative timing of said shafts, and mechanism controlled in synchronism with the variation of the relative timing of said shafts and operating in opposition to said device.

HAROLD HILLIER. JAMES COLQUHOUN MACFARLANE. WILLIAM ALLAN MACFARLANE. 

